Iliac artery aneurysms may cause ureteral obstruction. Six cases are reported. The major symptom is renal colic but a palpable aneurysm and a bruit may be found preoperatively and urinalysis may reveal microhematuria. On x-ray the ureter may be deviated medially, anteriorly or laterally. The ureter is bound down in a dense, desmoplastic reaction. All of our patients were treated by ureterolysis, with resection and grafting of the aneurysm in 4 of the 6.